The present invention relates to a method of controlling a bar supplying apparatus provided for a numerically controlled lathe, for continuously machining products while feeding a long bar on a predetermined length unit basis through a through hole in a main spindle.
A bar supplying apparatus for supplying a long bar through a through hole formed on the axis of a main spindle of a numerically controlled lathe (hereinbelow, described as NC lathe) is known. The bar supplying apparatus can continuously machine a plurality of products from a single bar by repeating a process of allowing the tip of the bar project by a predetermined length from a guide bush provided on the axis or in front of the main spindle, machining the tip of the bar with a tool attached to a tool post, cutting off a product from the tip of the bar by a cutting-off tool, feeding the bar by a predetermined length, and similarly machining the tip of the bar.
FIG. 9 shows the configuration of a conventional NC lathe having such a bar supplying apparatus.
As shown in the diagram, an NC lathe 110 has a headstock 113 which can move forward and backward in the same direction as the Z axis, a main spindle 112 rotatably supported by the headstock 113, in which a through hole 112a into which a bar W is inserted along a main spindle axis C is formed, a chuck 117 for holding the bar W, provided at the tip of the main spindle 112, a guide bush 116 provided in front of the headstock 113 (in the left part of FIG. 9), for rotatably supporting the tip of the bar W, and a tool post 114 to which a plurality of tools T are attached.
The tools T attached to the tool post 114 include not only a single point tool for machining the tip of the bar W projected from the guide bush 116 but also a cutting-off tool for cutting off a product formed at the tip of the bar W, and a positioning tool for positioning the bar W on the main spindle axis C by making the tip of the bar W fed from a bar supplying apparatus 120 to be described next come into contact with the tool.
An NC apparatus 115 of the NC lathe 110 controls travel of the headstock 113 and the tool post 114 in accordance with a machining program.
The bar supplying apparatus 120 for feeding the bar W to the NC lathe 110 is disposed rearward of the NC lathe 110 (in the right part of FIG. 9).
The bar supplying apparatus 120 has a not-illustrated bar housing for housing a plurality of bars W, a plurality of bar supporting units 128a, 128b, and 128c each for placing the bar W supplied from the bar housing on the main spindle axis C, and run-out preventing chucks 129a, 129b, and 129c provided for the bar supporting units 128a, 128b, and 128c, respectively, each for holding some midpoint of the bar W so that the long bar W is not bent at the time of machining the tip of the bar W. A similar run-out preventing chuck 129d is also provided on the rear end side of the main spindle 112 of the NC lathe 110.
In the rear part of the bar supplying apparatus 120, a feeder 123 for feeding the bar W placed on the bar supporting units 128a, 128b, and 128c toward the main spindle 112 is provided. At the tip of the feeder 123, a finger chuck 123a which holds the rear end of the bar W and rotates with the bar W is provided.
The feeder 123 is moved forward/backward in the main spindle axis C direction by a driving unit 121 constructed by a motor 121a, a pulley 121b rotated by the driving of the motor 121a, and a belt 121c running around the pulley 121b. 
Supply of the bar W from the bar housing, opening/closing of the run-out preventing chucks 129a, 129b, 129c, and 129d, and driving of the motor 121a are controlled by a control unit 125 provided for the bar supplying apparatus 120.
In the bar supplying apparatus 120 having the above configuration, it is necessary to prevent interference between the feeder 123 and the run-out preventing chucks 129a, 129b, 129c, and 129d at the time of feeding the bar W to the main spindle 112 and during the bar W is machined.
For this purpose, before automatic machining is started, the operator manually feeds the feeder 123 in the main spindle axis C direction to position the tip of the feeder 123 at the position 1, 2, 3, or 4 (refer to FIG. 9) before the run-out preventing chuck 129a, 129b, 129c, or 129d, respectively. The position of the feeder 123 at this time is stored in the control unit 125. When the feeder 123 is positioned at the position 1, 2, 3, or 4, the run-out preventing chuck 129a, 129b, 129c, or 129d corresponding to the position is set to be open.
Also, with respect to a timing of cutting the bar W short (which denotes cutting off of the tip portion of the bar having low machine accuracy at the start of machining on the supplied bar) and a timing of replacing the bar W, before the automatic machining is started, the feeder 123 is manually fed so that the tip of the feeder 123 is positioned in the timing position, and the position of the feeder 123 at this time is stored in a memory or the like of the control unit 125.
The flowchart of FIG. 10 shows the procedure of the above-described settings.
At the stage of setting before automatic machining is started, setting is started (step S100) and, simultaneously, a machining program is loaded to the NC apparatus 115 (step 101), and the number of products to be machined and the length of a bar are input (steps S102 and S103). A feed torque according to the length and diameter of the bar W is input to the control unit 125 of the bar supplying apparatus 120 (step S104).
Subsequently, a timing of opening the run-out preventing chucks 129a to 129d is input to the control unit 125 (step S105). As described above, the timing is input by manually feeding the feeder 123 to any of the positions 1 to 4 and inputting the coordinates of the feeder 123 at this time or the like. The positions 1 to 4 have to be determined in consideration of the maximum stroke of the headstock 113 during machining.
Similarly, the positions of the feeder 123 at the timing of replacing the bar W and timing of cutting the tip short are input to the control unit 125 (step 106).
Subsequently, data indicating whether the lengths of the bars W housed in the not illustrated bar housing are the same or not is entered (step S107).
After completion of the inputting operations, data setting is made, input values are stored in the NC apparatus 115 or the memory in the control unit 125 (step S108), and automatic machining is started (step S109).
However, in the conventional bar supplying apparatus 120, the operator has to manually feed the feeder 123 to one of the positions 1 to 4 and enter the coordinates or the like of the feeder 123 in the corresponding position to the control unit 125. Consequently, the work is troublesome and, moreover, there is a problem that long time is required since the bar W is set initially until the automatic machining starts.
The positions 1 to 4 which are set to prevent interference between the run-out preventing chucks 129a to 129d and the feeder 123 have to be determined in consideration of the maximum stroke of the headstock 113 at the time of machining the bar W. The operator has to determine the stoke on the basis of the length of a product and the machining program. It is consequently feared that, due to an improper determination, an unexpected situation such that the feeder 123 collides with the run-out preventing chucks 129a to 129d during machining or at the time of feeding the bar W arises.
The invention has been achieved in consideration of the problems and is to provide a method of controlling a bar supplying apparatus and a numerically controlled lathe which can realize automatic setting of the timing of opening a run-out preventing chuck, the timing of cutting a bar short, and the timing of replacing a bar by the minimum inputting work, shortened inputting and setting time, lessened work burden on the operator, and shortened machining time.
To solve the problems, the present invention provides a method of controlling a bar supplying apparatus provided for a numerically controlled lathe including: a headstock; a main spindle rotatably supported by the headstock and in which a through hole is formed along an axis; a tool post to which a tool for machining a bar projected from the main spindle through the through hole is attached; and a controller for controlling travel of the headstock or the tool post, and the bar supplying apparatus having a feeder for feeding the bar placed on a bar supporting unit toward the main spindle on a predetermined length unit basis, and a run-out preventing chuck for holding the bar supported on the axis by the bar supporting unit so as not to be run out to the side, wherein position data of the run-out preventing chuck, length data of the bar, length data in the axial direction of a product obtained by machining the bar, and dimensional data of cutting width for cutting the product off from the bar are preset in the controller, and the controller calculates the position of the feeder when the bar is positioned and when the bar is machined by feeder position calculating means and, on the basis of the calculated position of the feeder and each of the preset data, controls supply of the bar to the bar supporting unit, opening/closing of the run-out preventing chuck, and feeding of the bar.
According to the method, by an instruction of the controller of the NC lathe, a bar is supplied from the bar housing to the bar supporting unit. The bar placed on the bar supporting unit is held by the run-out preventing chuck so as not to be bent during automatic machining and when the bar is fed to the main spindle. The controller calculates the position of the feeder when the bar is positioned and when the bar is machined by feeder position calculating means and, and opens the run-out preventing chuck which may interfere with the feeder.
From the length data of a product and the dimensional data of cutting width, how much the bar is consumed by machining one product can be easily determined. The dimensional data of cutting width can be obtained from, for example, the width of a cutting-off tool. Therefore, by subtracting the length of the consumed bar from the original length of the bar, the length data of the machined bar can be obtained.
The length data of a product and the dimensional data of cutting width may be set by manual input of the operator or may be extracted from a machining program for machining a product.
As the feeder position calculating means, a servo mechanism or an encoder may be used. In this case, the position of the feeder can be calculated from the rotation angle of a rotary shaft of a motor, a pulley, or the like provided for the driving unit for moving the feeder.
The tip of the bar supported by the bar supporting unit is detected by detecting means positioned in a predetermined position, and the controller determines the position of the tip of the bar from the position of the feeder at the time when the detecting means detects the tip of the bar, length data of the product extracted from the machining program, and dimensional data of the cutting width, and controls feeding of the bar by the driving unit and opening/closing of the run-out preventing chuck.
In this manner, by the detecting means positioned in the predetermined position for detecting the tip of a bar, without inputting the length of the bar by the operator, the length can be automatically determined. Further, from the length of the bar obtained in the above manner and the position of the feeder detected by the servo mechanism or the like, the position of the tip of the bar can be easily obtained.
By using the servo motor, the feeder can be moved synchronously with movement of the bar in association with machining.
The feeder position calculating means is an arithmetic unit provided for the controller, the tip of the bar fed by the feeder is made come into contact with a contact member positioned in a predetermined position, thereby positioning the bar, and the arithmetic unit may calculate the position of the feeder on the basis of position data of the contact member, length data of the bar, length data of the product, and dimensional data of the cutting width.
According to the method, without using a servo motor or the like, the position of the feeder when the bar is positioned and when the bar is being machined can be obtained.
By making the tip of a bar come into contact with the contact member preliminarily positioned, the position of the tip of the feeder can be calculated from the position of the contact member and the length of the bar. By subtracting the length of a product and the width of a cutting-off tool from the initial length of the bar, the length of the bar after machining can be derived. From the position of the contact member and the length of the bar after machining, the movement amount of the feeder by the machining of the product can be obtained.
Further, the number of products to be machined may be preliminarily input to the controller, and the necessary number of the bars and an expected length of the remaining bar may be calculated on the basis of the number of products to be machined. In this case, whether or not the bar is machined until it is used up may be determined from the expected length of the remaining bar calculated on the basis of the number of products to be machined, from the expected length of the remaining bar calculated on the basis of the number of products to be machined.
A plurality of bars of different lengths are housed in a bar housing for housing the bars, the length data of the bars housed in the bar housing is preliminarily input to the controller, and the bar may be supplied from the bar housing so that expected length of the remaining bar becomes the minimum on the basis of the length data of the product and the number of products to be machined.
According to the method, the bar can be effectively used, and the machining cost can be reduced.
The object of the invention can be also achieved by a numerically controlled lathe having a controller for performing a control according to the control method.
Specifically, there is provided a numerically controlled lathe comprising a headstock, a main spindle rotatably supported by the headstock and in which a through hole is formed along the axis, a tool post to which a tool is attached, and a controller for controlling travel of the headstock or the tool post, wherein the tool of the tool post is provided separately from the numerically controlled lathe, a run-out preventing chuck for holding the bar so as not to be run out to the sides is provided in a preset position, and a bar supplied from a bar supplying apparatus through the through hole in the main spindle is machined by the tool of the tool post, the bar supplying apparatus having a feeder for feeding the bar toward the main spindle on a predetermined length unit basis, and the controller has a function of calculating the position of the feeder when the bar is positioned and when the bar is machined by feeder position calculating means, and controlling supply of the bar to the bar supporting unit, opening/closing of the run-out preventing chuck, and feeding of the bar on the basis of the calculated position of the feeder, length data in the axial direction of a preset product, and dimensional data of cutting width for cutting the product from the bar.
According to the invention, only by inputting the number of products to be machined, the timing of replacing a bar, the timing of cutting a bar short, an amount of feeding a bar, and the timing of opening/closing the run-out preventing chuck can be automatically controlled.